Endless track-propelled vehicles are widely known. These vehicles are primarily used as off-highway vehicles and are usually supported by walking beams arranged in pairs, such that each walking beam on one side of the vehicle is paired with another walking beam on the opposite side and such that a pair of wheel axles and wheels are secured to the opposite longitudinal ends of each walking beam. Such construction is conventionally used for relatively long and heavy endless track-propelled off-highway vehicles to produce the necessary load-bearing capacity (see U.S. Pat. No. 3,471,166 issued to E. G. Clark on Oct. 7, 1969).
It has been proposed by the present inventor, in his U.S. Pat. No. 5,076,378 issued on Dec. 31, 1991, to provide a suspension arrangement for off-highway vehicles wherein a front pair of walking beams and a rear pair of walking beams are joined end-to-end by a simple pivotal joint for positive and simple pivoting of the front beams relative to the rear beams about a transverse axis. In this patent, the inventor provides a telescopic arrangement of one pair of walking beams to allow for extension and contraction of those beams upon up-and-down pivoting of the pairs of walking beams. The shafts pivotally joining the walking beams to the frame of the vehicle are positioned strategically so that the same endless track length is needed substantially throughout the range of relative up-and-down pivotings of the front and rear walking beams.
However, since the telescopic arrangement of one pair of walking beams is located between the two shafts joining the walking beams to the frame of the vehicle, the tension imparted to the endless track is supported by the shafts. It is therefore necessary to provide shafts which are stronger and larger than usual to support this tension and the weight of the vehicle.
Furthermore, since the telescoping portion of one of the walking beams is provided at a location where shearing forces are generated by the up-and-down pivoting of the front and rear beams, premature wear may appear at the telescoping portion of one of the walking beams.
There is therefore a need, in a track tensioning system, for a walking beam arrangement for endless track-propelled vehicles which would ensure a substantially uniform tension on the endless track without causing premature wear to the walking beams.